Aptitude - Problems on Trains - Discussion

125/10 = 25/2

25/2*18/5 = 450/10
45

friends,
i don't know how to solve this problems after this
so plz anyone help me out

Just try this 1 sec 5 km/hr means 10 sec is 50 km/hr thats it..
becoz the man running at same time train is moving ..

To convert km/h into m/s we multiply that value with 5/18.why is this because
1km=1000m
1h=60min*60sec=3600sec
now
1km/h=1000/3600=5/18
if we want to convert m/s into km/h we have to multiply with 18/5.
hope you can understand.

Abisheks answer is realy nice. Thank you abi.

x-5 is nothing but here x refers to the speed of train and as both train and boy are moving in the same direction relative velocity comes into picture and here relative velocity is the difference of two velocities.

If train moving same direction = SUBTRACTION OCCUR.
If train moving opposite direction = ADDITION OCCUR.

Let the speed of the train is x km/hr
Then the relative speed is (x-5)km/hr
Therefore,
Time = 10sec
Distance = 125m
Speed = (x-5)km/hr
As we are calculating in m/sec so we have to convert km/hr to m/sec.
(x-5)*1000/3600 m/sec or (x-5)*5/18 {by cancelling by 200.
200*5=1000,200*18=3600}

Therefore ,

Speed = distance/ time
(x-5)5/18 = 125/10
x-5 = 125*18/10*5
x-5 = 2250/50
x-5 = 45
x = 45+5
x = 50
Therefore x is 50km/hr (speed of the train)

Hai friends I want to give small tips.

If there train passes in same direction just subtract it.

If train passes in different or opposite direction direction just add it. If you need to convert km/pr use this formula (a*5%18) for speed and m/sec the formula is (a*18%5).

Why you made it 18/5, earlier it was 5/18, please explain me.

Here x=45 is speed of per 1km. question is 5km/hr .
So
x-5=45
x=45+5
x=50
Thats all.